Liquid crystal display (LCD) is commonly used as a display device because of its capability of displaying images with good quality while using little power. An LCD apparatus includes an LCD panel formed with liquid crystal cells and pixel elements with each associating with a corresponding liquid crystal cell and having a liquid crystal capacitor and a storage capacitor, a thin film transistor (TFT) electrically coupled with the liquid crystal capacitor and the storage capacitor. These pixel elements are substantially arranged in the form of a matrix having a number of pixel rows and a number of pixel columns. Typically, scanning signals are sequentially applied to the number of pixel rows for sequentially turning on the pixel elements row-by-row. When a scanning signal is applied to a pixel row to turn on corresponding TFTs of the pixel elements of a pixel row, source signals (image signals) for the pixel row are simultaneously applied to the number of pixel columns so as to charge the corresponding liquid crystal capacitor and storage capacitor of the pixel row for aligning orientations of the corresponding liquid crystal cells associated with the pixel row to control light transmittance therethrough. By repeating the procedure for all pixel rows, all pixel elements are supplied with corresponding source signals of the image signal, thereby displaying the image signal thereon.
Liquid crystal molecules have a definite orientational alignment as a result of their long, thin shapes. The orientations of liquid crystal molecules in liquid crystal cells of an LCD panel play a crucial role in the transmittance of light therethrough. For example, in a twist nematic (TN) LCD, when the liquid crystal molecules are in its tilted orientation, light from the direction of incidence is subject to various different indexes of reflection. Since the functionality of LCDs is based on the birefringence effect, the transmittance of light will vary with different viewing angles. Due to such differences in light transmission, optimum viewing of an LCD is limited within a narrow viewing angle. The limited viewing angle of LCDs is one of the major disadvantages associated with the LCDs and is a major factor in restricting applications of the LCDs.
Several approaches exist for increasing the viewing angles of LCDs, such as in-plane switching (IPS), and multi-domain vertical alignments. The IPS mode uses comb-like inter-digitized electrodes to apply electrical fields in the plane of the substrates, thereby aligning the liquid crystal molecules along the substrates and providing wide viewing angles for use in wide viewing angle monitors or other applications. However, although IPS provides wide viewing angles, it requires high voltages and has low aperture ratios. In addition, due to the planar electric field structure, IPS mode inherently suffers from severe image sticking.
The vertical alignment mode uses a liquid crystal material with the negative dielectric anisotropy and vertical alignment films. When no voltage is applied to the mode, liquid crystal molecules are aligned in a vertical direction and no light passes through the liquid crystal molecules and therefore a black display appears. When a predetermined voltage is applied, the liquid crystal molecules are aligned in a horizontal direction and light passes through the liquid crystal molecules and a white display appears. The vertical alignment mode provides a high contrast ratio of display and a fast response speed. Furthermore, a multi-domain arrangement is achieved by introducing a protruding structure that forces the liquid crystal molecules to tilt in different directions, thereby providing an excellent viewing angle characteristic for white display and black display. As shown in FIG. 6, a conventionally vertical alignment mode 600 utilizes a layer 610 with a protrusion structure 612 formed on a color filter substrate 620 to divide liquid crystal domains. As a result, it requires an extra photolithography step during fabrication, and thus increases production cost. Additionally, the protruding structure 612 may make the contrast ratio of display lower due to the light leakage in the black display.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.